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Graphics Cards

Journeyman III

Dual GPU issues on Linux (IOMMU issues maybe?)

Hey Guys,

I have an issue. Here is my system description:

AMD Ryzen 7 1700

ASRock AB350M Pro4 (5.7 latest BIOS)

32 GB RAM DDR4 Crucial

Sapphire AMD Radeon RX 550 PULSE 2GB GDDR5 128bit

Sapphire AMD Radeon RX 580 Nitro+ Special Edition 8GB GDDR5 256bit

SSD 240 GB WD Green

OS: CentOS 7.6 Linux

The system is mainly used for Linux development and cloud configuration (using RDO), but every now and then, I am doing some renderings in Blender.

Two days ago I bought the second Sapphire GPU (the RX 580), thus thinking about using both for some blender rendering. I get a 30% increase in rendering time (tested in Win 10 on the same configuration).

Due to ASRock's motherboard slot configuration, I had to put the RX 550 on PCIe slot 2 (working as PCIe 3.0 x8) and the RX580 on slot 3 (working as PCIe 2.0 x4).  BIOS was configured to use the PCIe as 2x8 (not 1x16) and the PCIe speed set to auto. But... during startup, I had the following error messages (see the attached images).

To overcome the errors, I had to deactivate the IOMMU support from the BIOS, which led to a useable system, but only with the open source amdgpu driver from the kernel. After installing the official amdgpu-pro driver, with the current configuration, Xorg just refused to work.

Furthermore, turning off IOMMU somehow crippled my KVM and Docker configuration and workflow.

I would like some help from your side. Did anyone encounter this kind of issues using Linux with a dual GPU configuration?


1 Reply
Journeyman III

Hey billy72

Thanks for your reply.

Now, I don't believe that the issue is with the ASRock motherboard. 

I had the same error results with a new configuration:

CPU: Ryzen 7 1700

MB: Gigabyte B450 Aorus M (with the latest F5 bios firmware)


GPU1: Sapphire Radeon RX 580 Nitro+ Special Edition 8GB GDDR5

GPU2: Asus Mining Radeon RX 470 4G GDDR5

This time, the RX580 is on pcie 1 (3.0 x16) and the RX470 is on pcie 3 (2.0 x4). 

In both motherboards descriptions there is a special reference to suppport for dual GPU (and CrossFireX and Quad CrossFireX). 

By the way, both configuations work perfect under Windows 10, I only have issues with CentOS 7, Ubuntu 18.04 and Fedora 29...

Until now, now success with installing Linux on those configurations...